Temp gauge flucuation?

[Hogan]

Long time visitor, first time owner and poster. #ad
Got a question, I've got a '97 with 127k miles and I noticed today that the temp gauge, once warmed up, will drop down to the bottom of the normal zone (150F?) within about 5 seconds, then slowly climb back up to about 185F to 190F over the course of 30-45 seconds, then it'll stay there for a few seconds and the cycle starts all over again. Somehow I don't think my engine is cooling off that much that quickly and that often. #ad
Has anyone else had this happen? Maybe a bad ground or temp sensor? It always drops down to the exact same temp. I'm not super concerned about it as long as the upper temp it reaches is accurate, but at this point I don't know. Thanks! Love the truck (and the gas mileage!)

 

[Joe G.]

Normal behaviour. This subject has been chewed a lot. Do a search on the archives and you will find a lot more than you want to read. This is especially noticable in the winter. What is happening is that the coolant warms up enuff to open the stat. Then the coolant from the very large radiator that has been dropping in temp in all that cold wind for some time comes into the engine. This causes the drop in the gage reading. (I don't think the iron is varying quite that much in temp. ) That closes the stat so the cycle starts over again.

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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,BD valve body,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver

 

[Hogan]

Thanks Joe! I wouldn've have thought it would cool so much so fast, but then again, with what it can tow it's gotta have some wicked cooling. #ad


Reading and learning... #ad

 

[illflem]

Hogan,it sounds like even in a "warm"climate like Stockton you could benefit by blocking your radiator front. Use cardboard,it's cheap and easy to find. It will smooth out the normal thermostat cycling you are seeing and give you faster,hotter heater output. Click here,this thread has much info

 

[Bob V]

My '97 did the same thing untill I replaced the thermostat with the latest revision from Cummins. Genoes has the best price I have found.

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'97 CC 5spd 4. 10 5spd 315/75 16,Bushwacker,TST 280hp.